That means that the species do not exist in a big number and their size is likely to decrease further and the species may become extinct. It means that if the current situation continues then there will not be any more of those species after some years future.
Due to human life styles, hunting, pollution and other factors, existence of some species are being threatened on Earth.
Some birds, and some animals were identified as threatened all over the world. To save them, special biological parks are established to allow the species to breed and grow, and to prevent human intervention in their life.